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Abstrak :
ABSTRAK Suatu teknik yang relatip baru untuk mensimulasikan open boundary telah diterapkan pada penyelesaian persoalan elektromagnet tiga dimensi dengan menggunakan metode elemen hingga berbasis elemen tetrahedral vektor. Teknik ini disebut juga teknik PML karena menggunakan material PML atau Perfectly Matched Layer. Material PML ini mempunyai sifat anisotropis pada arah diagonal. Material PML bersifat loss-y, sehingga gelombang elektromagnet yang berasal dari udara babas akan diteruskan dan diredam secara eksponensial. Secara teoritis, koefisien refleksi pada perbatasan antara medium udara dengan medium PML adalah nol. Karakteristik medium PML dinyatakan dalam parameter α dan β. Konstanta α menentukan panjang gelombang pada medium PML, sedangkan menentukan laju peredarnan gelombang elektromagnet yang diteruskan. Teknik PML ini diterapkan pada open waveguide persegi ernpat. Pemodelan open boundary dilakukan dengan menggunakan kode program EMAP, yang merupakan kode pemodelan elemen hingga tiga dimensi. Kode program pemodelan open boundary ini dibuat dalam bahasa C. Konfrgurasi masukan yang diberikan ke kode program berupa file berbentuk teks atau numerik, dan menghasilkan keluaran dengan format yang sama dengan masukan. Keluaran dari kode program merupakan sekumpulan data numerik berupa titik-titik koordinat di seluruh domain komputasi dan distribusi medan listriknya. Perangkat lunak Jandel Sigma Plot 3.0 digunakan untuk memvisualisasikan data numerik Sedangkan, paket program pengolah data Microsoft Excell digunakan agar formal keluaran yang dihasilkan oleh kode program sesuai dengan format perangkat lunak Sigma Plot 3.0. Eksperimen numerik dilakukan untuk mengetahul distribusi medan listrik di dalam waveguide persegi empat pada berbagai ketebalan lapisan PML. Selanjutnya hasil eksperimen tersebut tersebut dibandingkan dengan penyelesalan secara analitis. Mode eksitasi yang digunakan adalah mode dominan TE10 dan TE20. Hasil perhitungan numerik tersebut menunjukan bahwa nilai koefisien refleksi berbanding terbalik dengan ketebalan lapisan PML. Semakin tebal lapisan PML maka nilai koefsien refleksi pada perbatasan antara medium udara dengan medium PML akan semakin kecil. Pada ketebalan lapisan antara 4 s/d 16 PML diperoleh rugi-rugi antara 4.00 db s/d 33.73 db. Ketebalan lapisan PML dinyatakan dalam jumlah elemen. Eksperimen numerik lalnnya dilakukan untuk menghilung pengaruh konstanta α dan β dari medium PML terhadap distribusi medan listrik pada domain komputasi.

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ABSTRACT A newly used technique offree space simulation has been implemented for solving unbounded electromagnetics problems with the finite element method based on tetrahedral edge or vector element. This technique uses a layer of diagonally anisotropic material referred to as a PML. The PML layers are lossy, so the outgoing waves from the computation domain will be absorbed, and exponentially atenuated. The PML itself can be characterized by a and ,B, where adetermines the wave length in the anisotropic absorber and /7 determines the rate of decay of the transmitted wave. Eventhough, the material properties can be chosen such that the interface between the absorbing material and free space is reflection-less, but a numerical reflection error must be taken into account. An open rectangular waveguide is used as a model to investigate the PML technique. The modelling is carried out using EMAP, which is a three dimensional finite element modelling code that can be used to simulate open region, and written in the C programming language. The code reads the input configuration in as an ASCII text file, and provides output in the same form. Output from the code consist of a listing of the node coordinates and the electric field strength at each node. These numerical data are not easily understood, so a post processing is needed to manipulate them into a graphical output. To do this, the data are rearranged by the spreadsheet Microsoft Excel , and then plotted by dandel Sigma Plot 3.0 for a visualization. A number of experiments is carried out to investigate the electric field distribution in the computation domain. The results show that after a few layers the electromagnetic wave is exponentially attenuated through the PML material. Then, the numerical results are compared to the analytical solution. These numerical results may be important in determining the number of PML layers needed to obtain a given accuracy. It can be seen that the reflection is reciprocal of the number of layers. The reflection coefficient is decreased by increasing the layer thickness. A thickness of 4 to 16 PML layers have loss in the range of 4.00 db to 33.73 dh. The layer thicknes itse f is represented in term of a number of elements. Another experiment is also done to investigate the electric field distribution in the computation domain with varied in ca and A It is concluded that the PMLs work well to model an open rectangular waveguide.

Abstrak :
ABSTRAK
Pengujian elektrokimia menjadi salah satu pengujian yang digemari dalam bidang korosi. Salah satu pengujian yang cukup terkenal saat ini adalah Electrochemical Impedance Spectroscopy dimana menggunakan sistem listrik untuk menganalisis suatu material dalam sistem tertentu. Penerapan metode numerik untuk EIS memungkinkan pengujian EIS dapat dilakukan secara pemodelan untuk kasus-kasus dimana sampel material susah untuk diambil ataupun dilakukan pengujian secara insitu

Pelaksanaan pemodelan numerik pada penelitian ini dibantu dengan metode elemen batas. Respon EIS berupa arus akan di cari dengan mengaplikasikan potensial pada model 2D berbentuk persegi panjang, dengan mendiskritisasikan dengan elemen konstan menjadi 15 elemen. Laplace digunakan sebagai persamaan pembangun, akibat dari sistem yang homogen dan sifat elektronetrality sistem. Respon dari model selanjutnya di terjemahkan dalam bentuk impedansi dan dalam plot Nyquist. Impedansi hasil model numerik ini selanjutnya akan dibandingkan dengan hasil pengujian EIS

Model yang di dapatkan pada penelitian ini secara umum dapat digunakan untuk studi awal dalam memodelkan EIS. Bentuk grafik plot Nyquist terlihat perbedaan yang signifikan. Beberapa perlakuan tambahan harus dilakukan pada tahapan matematis dari model dan penggunaan metode lain pada sistem pengubah respon arus menjadi impedansi.

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ABSTRACT
Electrochemical testing become one of popular testing in corrosion study. One of testing is Electrochemicial Impedance Spectroscopy where used electrical system to analyze material in certain system. Implementation of numerical method for EIS is hoped to enable EIS testing conducted only in computation model, escpecially for case where the material is hard to be taken or in situ testing impossible to be conducted.

Numerical modeling in this research is helped by Boundary Element Method. Current as EIS respon is determined by applied potential input in 2D rectangular model, and disctritized by constant element to 15 parts. Laplace equation is used as governing equation as result homogenous and electroneutrality in model system. Model respons is translated to impedance as function of frequency then ploted in Nyquist plot diagram. The result of model impedance is compared to result of experimentally EIS testing

In general, the model could be used as basic study in EIS modeling. Though it has a significant difference between the experimental model, but the shape is follow the common semicircle of Nyquist plot. Some treatment can be conducted in mathematics step of numerical modeling and transferring response to impedance methods

Abstrak :
ABSTRAK
Suatu simulasi telah dilakukan mempelajari sifat optik dari nanopartikel emas bentuk batang (gold nanorod) menggunakan metode elemen batas (boundary element method-BEM), dalam kasus ini kita akan memperhitungkan tidak hanya pengetahuan bahwa peningkatan medan oleh plasmon nanopartikel dapat mempengaruhi respon optic tetapi juga plasmon sangat sensitive terhadap perubahan dielektrik dari lingkungan, dengan demikian sifatnya juga dipengaruhi oleh bentuk dan ukuran dari nanopartikel. Kami menemukan bahwa, Puncak-puncak spektrum ekstinsi, hamburan dan absorpsi terhadap panjang gelombang mengalami pergeseran ke arah panjang gelombang besar(red-shift) dengan bertambahnya ukuran diameter dari nanopartikel emas demikian juga dengan peningkatan indeks bias, sedangkan puncak-puncak spektrum ini mengalami pergeseran ke arah panjang gelombang kecil (blue-shift) dengan bertambahnya aspek rasio (AR) dari nanopartikel emas.

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ABSTRACT
A simulation has been performed to study the optical properties of gold nanoparticles form of rods (gold nanorod) using the boundary element method (BEM boundary-element method), in this case we will take into account not only the knowledge that increasing the field by plasmon nanoparticles can affect the optical response but also the plasmon very sensitive to changes in the dielectric of the environment, thus its also influenced by the shape and size of nanoparticles. We found that, extinction spectrum peaks, scattering and absorption wavelength shifted toward large wavelengths (red-shift) with increasing the diameter of the gold nanoparticles as well as an increase in the refractive index, while the peaks of this spectrum shifted towards smaller wavelengths (blue-shift) with increasing aspect ratio (AR) of the gold nanoparticles.

Abstrak :
Telah diamati pengaruh konfigurasi dimer AgNR yaitu side by side dan end to end terhadap sifat optis Localized surface plasmon resonance dengan menggunakan pendekatan boundary element method. Medium yang digunakan pada penelitian ini adalah air dengan indeks bias sebesar 1.334. Variasi aspek rasio nanorod 1 hingga 5 dilakukan untuk mengetahui pengaruhnya terhadap pergeseran puncak LSPR serta juga dilakukan variasi jarak pisah antar nanorod perak. Fungsi dielektrik perak menggunakan hasil percobaan Johnson Christy. Dengan memvariasikan arah medan listrik sejajar sumbu utama nanorod mode Longtudinal dan tegak lurus sumbu utama nanorod mode Transversal didapati bahwa pergeseran puncak LSPR selain bergantung pada jarak pisah antar coupling nanorod namun juga terhadap konfigurasi dimer AgNR yang masing-maing memiliki 2 mode yaitu Transversal dan Longitudinal yang muncul akibat asimetri bentuk nanorod. Pada konfigurasi end to end mode Transversal pergeseran puncak LSPR cendrung bergeser ke arah panjang gelombang yang lebih pendek Blue-shift seiring dengan pengurangan jarak pisah antar nanorod dan pada mode Longitudinal didapati pegeseran puncak LSPR mengalami Red-shift. Sedangkan pada konfigurasi side by side memperlihatkan fenomena pergeseran puncak LSPR yang berkebalikan dengan konfigurasi end to end untuk mode Transversal dan Longitudinal. Ketergantungan pergeseran puncak LSPR terhadap konfigurasi dimer AgNR ini bisa dijelaskan secara kualitatif melalui interakasi dipole-dipole antar nanorod yang berdekatan. ...... It has been observed that the influence of AgNR dimer configurations which side by side and end to end on optical properties of Localized surface plasmon resonance by using boundary element method approach. The medium used in this reasearch was water with a refractive index of 1,334. Variations in nanorod aspect ratio 1 to 5 were performed to determine the effect on the LSPR peak shift as well as the variation of separations between silver nanorods. The silver dielectric function based on Johnson Christy 39 s experimental results. By varying the direction of the electric field parallel to the main axis of nanorod Longtudinal mode and perpendicular to the main axis Transverse mode , that two modes arising from the asymmetry of nanorod shape. it is found that the peak shift of LSPR is dependent on the spacing between the nanorod coupling but also the configuration of the AgNR dimer. For end to end assembly, Transversal mode shows that LSPR peak shift tends to shift towards the shorter wavelength Blue shift along with the reduction of the spacing between the nanorod and for Longitudinal mode LSPR peak shift has Red shifted. While for side by side configuration shows the phenomenon of LSPR peak shift in contrast to the configuration of end to end for Transverse and Longitudinal modes. The dependence of the LSPR peak shift to this AgNR dimer configuration can be explained qualitatively through dipole dipole coupling interaction between adjacent nanorods.

Abstrak :
This self-contained book addresses the three most popular computational methods in CAE (finite elements, boundary elements, collocation methods) in a unified way, bridging the gap between CAD and CAE. It includes applications to a broad spectrum of engineering (benchmark) application problems, such as elasto-statics/dynamics and potential problems (thermal, acoustics, electrostatics). It also provides a large number of test cases, with full documentation of original sources, making it a valuable resource for any student or researcher in FEA-related areas.

Abstrak :
This volume covers diverse areas of applied mathematics, continuum mechanics, stress analysis, and mechanical design. This work treats a number of topics not presented in other books on thermal stresses, for example: theory of coupled and generalized thermoelasticity, finite and boundary element method in generalized thermoelasticity, thermal stresses in functionally graded structures, and thermal expansions of piping systems. The book starts from basic concepts and principles, and these are developed to more advanced levels as the text progresses. Nevertheless, some basic knowledge on the part of the reader is expected in classical mechanics, stress analysis, and mathematics, including vector and cartesian tensor analysis. This 2nd enhanced edition includes a new chapter on Thermally Induced Vibrations. The method of stiffness is added to Chapter 7. The variational principle for the Green-Lindsay and Green-Naghdi models have been added to Chapter 2 and equations of motion and compatibility equations in spherical coordinates to Chapter 3. Additional problems at the end of chapters were added.

Abstrak :
This book contains manuscripts of topics related to numerical modeling in Civil Engineering (Volume 1) as part of the proceedings of the 1st International Conference on Numerical Modeling in Engineering (NME 2018), which was held in the city of Ghent, Belgium. The overall objective of the conference is to bring together international scientists and engineers in academia and industry in fields related to advanced numerical techniques, such as FEM, BEM, IGA, etc., and their applications to a wide range of engineering disciplines. This volume covers industrial engineering applications of numerical simulations to Civil Engineering, including: Bridges and dams, Cyclic loading, Fluid dynamics, Structural mechanics, Geotechnical engineering, Thermal analysis, Reinforced concrete structures, Steel structures, Composite structures.

Abstrak :
This book gathers outstanding papers on numerical modeling in Mechanical Engineering (Volume 2) as part of the proceedings of the 1st International Conference on Numerical Modeling in Engineering (NME 2018), which was held in Ghent, Belgium. The overall objective of the conference was to bring together international scientists and engineers in academia and industry from fields related to advanced numerical techniques, such as the finite element method (FEM), boundary element method (BEM), isogeometric analysis (IGA), etc., and their applications to a wide range of engineering disciplines. This book addresses various industrial engineering applications of numerical simulations to Mechanical and Materials Engineering, including: Aerospace applications, Acoustic analysis, Biomechanical applications, Contact problems and wear, Heat transfer analysis, Vibration and dynamics, Transient analysis, Nonlinear analysis, Composite materials, Polymers, Metal alloys, Fracture mechanics, Fatigue of materials, Creep behavior, Phase transformation, and Crystal plasticity.